Absolutely relatable. It's funny how low-budget clients have more audacity to be demanding haha. The best clients are just chill. My first client paid me my first month salary in advance without a contract. But be careful of others, too. I guess I was just lucky.
When Fiverr and Upwork didn't work for me. I joined Facebook and Linkedin groups. I also joined Reddit communities (altho i haven't had a client from there yet). In your case, your niche is medicine. So, join FB groups where doctors are lurking. Observe the posts, maybe they're conveying a problem that you can help in solving. Keep commenting in the posts and provide value. They'll notice you. And they'll think you're an expert coz you know what you're talking about.
As for me, I found my first client in an FB group for copywriting jobs. She was a VA for the client. She said she's looking for a finance blog writer. I went ahead and gave her a message. I told her why I'm in the position to help, and I offered to do a discounted test article 😊